In order to save some energy, one decision our lab is examining would be to increase the temperature limit of the freezers at -70°C instead of -80°C. I guess 10°C difference in this very low temperatures may help to save substantial amount of energy supply. Therefore, we are wondering if samples can be stored at this temperature without causing any remaining molecular activities (oxidative stress and so on).
It is not super clear in the litterature why this threshold of -80°C has been selected, does it result from empirical measures or not?
If anyone has an idea on the reasons for the choice of -80°C, this could help us to take the best decision.
Thanks in advance
Hello Andréaz Dupoué
Yes, you may store samples for molecular biology and biochemical assays at -70 degree C instead of -80 degree C. It will reduce energy consumption by 30-40%, thus helping to save substantial amount of energy supply. Nucleic acids can be safely stored at -20 degree C, or -70 degree C, depending on how long they need to be stored, and most proteins can be safely stored at -70 degree C. Bacteria and viruses are also generally safe at -70 degree C.
In fact, if you look back in time all ultra-low freezers were set to -65 degree C or -70 degree C. For samples to be stored at – 80 degree C, the acceptable temperature range is -70 degree C to -93 degree C.
So, go ahead and store your samples for molecular biology and biochemical assays at -70 degree C.
Best.
I believe storage at around -80 has been convenient to me, because I avoid considering effects of temperature changes when transporting samples on dry ice. Maybe that's the reason for the choice of -80?
The choice of -80°C as a freezer temperature for long-term storage of biological samples is a widely accepted standard that has been empirically established through many years of research and experience. It is believed to ensure that biological samples remain stable over time and that molecular activities, such as oxidative stress, are minimized.
While increasing the freezer temperature to -70°C may save energy, it is not recommended as it can potentially result in the degradation of biological samples over time. At -70°C, some cellular processes, such as oxidation and enzymatic activity, can still occur, although at a slower rate compared to warmer temperatures. However, it is important to keep in mind that the stability of biological samples depends on many factors, including the type of sample, the storage conditions, and the length of time in storage.
If you are considering changing the freezer temperature, it is recommended to perform a risk assessment to determine the potential impact on your samples. You can consider running a pilot study to assess the stability of a representative subset of your samples stored at -70°C over a period of time, and then comparing the results to samples stored at -80°C. You may also want to consult with experts in the field, such as cryobiologists or biorepository managers, for advice and guidance.
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